A consolidated view of the evolution of the state of fluctuations is provided in phase space [1]}, [2]}, [3]}, [4]}. In the phase-space portrait, one axis measures the buoyancy effect on the large scales through the turbulent Froude number (\(Fr_h\) ) and the other axis is a measure of Reynolds number that is not \(Re_h\)  but one which accounts for buoyancy in addition to inertia. Ozmidov-scale eddies are the largest eddies unrestrained by buoyancy. The Ozmidov scales \(l_o=(\varepsilon /N^3)^{1/2}\)  and \(u_o=(\varepsilon /N)^{1/2}\)  lead to the definition of \(_b=u_ol_o/\nu = \varepsilon /\nu N^2\)  as the so-called buoyancy Reynolds number. Another convenient measure of Reynolds number, which does not require explicit computation of the turbulent dissipation rate, is the buoyancy-weighted Reynolds number, \(Re_h\mbox{\textit {Fr}}_h^2\)  [5]}, [6]}. The Reynolds numbers based on buoyancy tend to decrease with downstream distance as buoyancy progressively increases in importance and limits the range of scales which are susceptible to 3D turbulent motions. As long as \(Re_h\mbox{\textit {Fr}}_h^2 > O(1)\) , viscous effects do not dominate.
